Molded stem



Feb. 9, 1943. c. A. HORN 2,310,237

MOLDED STEM Filed Feb. 24, 1939 INvENToR CLARENCE A. HORN ATTORNEYPatented Feb. 9, 1943 MOLDED STEM Clarence A. Horn, Newton, Massassignor. to

Raytheon Production Corporation, Masa, a corporation of Delaware Newton,

Application February 24, 1939, Serial No. 258,283

4 Claims. (Cl. 250.2'l.5)

This invention relates to electrical discharge devices comprising sealedenvelopes, such as electron discharge devices and the like, and moreparticularly to a novel stem for such devices.

Attempts have been made to produce electron discharge tubes with glassenvelopes in which the stem serves as the tube base itself, and whichcarries lead-in conductors which also serve as the external contactpins. Difficulties have been encountered in constructing a. stem whichreadily cou d be sealed to the envelope.

An object of this invention is to devise a stem of the foregoing typewhich can be sealed to an envelope in a simple, inexpensive and reliablemanner.

Another object is to devise such a stem which is inexpensive tomanufacture.

The foregoing and other objects of this invention will be bestunderstood from the following description of an exemplification thereof,reference being had to the accompanying drawing, wherein:

Fig. 1 is a perspective view, partly broken away, of an electrondischarge tube incorporating my novel stem;

Fig. 2 is a top view of a stem made in accordance with the presentinvention;

Fig. 3 is a section taken along line 33 of Fig. 2; and

Fig. 4 is a section taken along line 4--4 of F18. 2.

The tube as illustrated in Fig. 1 consists of a glass envelope I havinga bottom wall consisting of a stem or base 2. A plurality of lead-inrods 3 are sealed through said stem 2. lead-in rods are made of somemetal which readily seals to the glass of said stem, and mayconveniently be made of chrome iron. The lead-in rods 3 are disposed ina circle concentric with the center of the stem 2. These lead-in rodsare also rigid so that in the completed form of the tube they serve asthe external contact pins adapted to be inserted into a cooperating tubesocket. If desired a number of dummy support wires 4 may likewise besealed into the upper surface of the stem 2. These dummy support wiresdo not extend through the stem, and therefore need not form an air-tightseal therewith. For this purpose these dummy support wires may be madeof a metal which does not make a perfect seal with the glass. They mayconveniently be formed of nickel. The usual type of mount 5 is supportedby the lead-in rods 3 and the dummy support wires 4. The mount 5 mayconsist of a plurality of electrodes, for example, an anode 8 Thesesurrounding a cathode I. In order to enable the tube to be exhausted,the stem 2 is provided at its central portion with an exhaust openingcommunicating with an exhaust tube 8. The bottom of the tube issurrounded by a guard shell 9 held in place on the tube by means of aring of cement Ill. The guard shell 8 is provided with a central tubularmember I I which surrounds and protects the portion of the exhaust tuberemaining on the completed tube. The guard shell 8 is provided withsufiiciently large openings around each of the lead-in rods 3 so thatelectrical contact between the shell 9 and the rods 3 is effectivelyprevented.

The tube, as illustrated in Fig. 1, is adapted to be inserted in asuitable tube socket, the tubular member I I cooperating with somesuitable locking arrangement, and the pins 3 cooperating with suitablecontact members in said socket, whereby the proper electricalconnections may be made to the electrode elements within the envelope I.

A tube of the foregoing type presents certain diillculties andrequirements if such an arrangement is to be commercially successful.Since the lead-in rods 3 serve as the external contact members for thetube, they must be kept parallel and maintained accurately in theirpredetermined circular relationship in order that such tubes may fitinterchangeably in standard sockets provided therefor. The glass of thestem must not extend too far up or down along the lead-in rods 3. Glassextending down along the lead-in rod 3 might well interfere with theproper insertion of the tube into its socket. Glass extending along saidrod 3 in either direction to an excessive degree produces a tendency forcracks to occur at the lead-in rods. Another requirement is that thestem 2 may be easily sealed to the envelope I by the usual type ofsealing-in machine. A further requirement is that during this sealing-inprocess, the main body of the stem 2 carrying the lead-in rods 3 shallnot be subjected to any distortion which might tend to upset therequisite positional accuracy of said lead-in rods. Stems made inaccordance with my present invention satisfy each of these requirements,and produce a tube which satisfies all of the objects of my invention asstated above.

My novel stem consists of a substantially flat disk of glass having acentral thickened portion I2 into which the lead-in rods 3 and the dummysupport wires 4 are sealed. This thickened portion must be sufllcientlystrong to withstand atmospheric pressure exerted on its lower flatsurface upon completlon of the tube. It must also be thick enough tofirmly and definitely support I and .095 of an inch. However,thicknesses as low as .060 might be feasible in some instances.Surrounding the thickened portion I2 is a thinned edge IS. The top ofthis edge I3 is preferably disposed in the same plane as the top of II,for reasons which willbe explained below. This thinned edge l3 must havea thickness sufflciently less than that of the central portion l2, sothat during the sealing-in process it can soften sufliciently to sealreadily to the glass. envelope i without producing any appreciablesoftening of the central portion I2. I have found that the thickness ofthe edge l3 conveniently may be made about half of the thickness of thecentral portion l2. In a particular instance I have used .045 to .055 asa thickness ofsaid edge. In the particular examples which I have cited,the thickness of the wall of the glass envelope l was between .030 and.050 of an inch. The stem 2 is preferably formed with a lower boss llaround each lead-in rod 3, and a smaller upper boss it around eachofsaid lead-in rods. The bosses l4 project through the openings in theguard shell 9, and thus maintain said guard shell in its proper positionas well as insure against electrical contact between said guard shelland the lead-in rods. The bosses H are slightly recessed around the rods8, as shown most clearly in Fig. 4.

After the stem has been completed, the mount 5 is assembled on thelead-in rods 8 and dummy support wires 4. The envelope I is then sealedto the stem around the mount.

I have found that tubes made in accordance with my invention producesatisfactory seals which have very little tendency to crack at thesealing-in point 46. This is due partly to various aspects of theinvention pointed out above in= volving the thickened central portion I2and thinned edge It of the stem 2. I have found that if the internalsurface of the envelope adjacent the sealing-in point 46 (see Fig. 1) iskept free of all sharp bends and a smooth and rounded contour preserved,substantially all tendency to crack at this point will be eliminated. Byforming the stem 2 with the thinned edge i3 in the same plane as theupper surface of said stem, this elimination of sharp bends and thepreservation of a smooth contour are readily obtained, since due to theparticular construction which I have described, when the edge i3 is madeplastic during the sealing-in process, the wall of the envelope willfuse to this thinned edge I3 and form a continuation thereof. During thepulldown operation, the thinned edge l3 will have some slight tendencyto be bent upwardly, thus producing a smooth transition curve from thethinned edge I3 to the interior walls of the envelope. Since the edge I3is originally formed as a continuation of the upper surface of the stem2, this smooth transition will be carried down without break orinterruption onto the upper surface of said stem 2, as indicated mostclearly in Fig. 1. Even if said edge I! were not formed in this way, therequisite sealing might still be accomplished with proper precautions.'I'hus considerable advantage is still obtained from the thinned edge I!irrespective of its relationghip with respect to either surface of thestem The method of making the stem described herein is claimed in myeo-pending application, Serial No. 269,871, filed April 25, 1939, whichis a division of the present case, Serial No. 258,263.

Of course it is to be imderstood that this invention is not limited tothe particular details as described above as many equivalents willsuggest themselves to those skilled in the art. For example, in someinstances it may be desired to utilize this invention in tubes havingthe conventional base with additional contacting prongs. Various otherchanges will suggest themselves to those skilled in the art. It isaccordingly desired that the appended claims be given a broadinterpretation commensurate with the scope of the invention within theart.

What is claimed is:

1. In combination, a stem assembly for electric tubes comprising arelatively thick glass wall member having substantially flat parallelupper and lower surfaces and a relatively t glass sealing edgeprojecting from said wall member, and a plurality of lead-in conductorssealed into said wall member, and a glass envelope sealed only to theouter edge of said sealing edge.

2. In combination, a stem assembly for electric tubes comprising arelatively thick glass member having substantially flat parallel upperand lower surfaces and a relatively thin glass sealing edge projectingfrom said wall member, and a plurality of lead-in conductors sealed intosaid wall member, said conductors being parallel to each other andhaving their I lower ends disposed in a plane, and a glass envelopesealed only to the outer edge of said sealing edge.

8. In combination, a stem for electric tubes comprising arelatively-thick, substantially-flat glass wall member, a relativelythin glass sealing edge projecting from said wall member, the thicknessof said sealing edge at the point where it joins said wall member beingsubstantially less than the thicmess of said wall member, the topsurface of said sealing edge lying in substantially the same plane asthe top surface of said wall member, and a plurality of lead-inconductors sealed into said wall member, and a glass envelope sealedonly to the outer edge of said sealing edge.

4. In combination, a stem assembly for electric tubes comprising arelatively thick glass wall member having substantially fiat parallelupper and lower surfaces, and a glass sealing edge having a thickness atthe point where it joins said wall member substantially less than thethickness of said wall member and projecting from said wall member asubstantial distance with substantially uniform thickness, a pluralityof lead-in conductors sealed through said wall member, and a glassenvelope sealed only to the outer edge of said sealing edge.

CLARENCE A. HORN.

